. >>> good evening, he is the most prominent and best-known general of the modern era, david petraeus, with so much over the combat strategy over the past ten days. when rumors suched he may be stepping down as head of the cia, some speculated he was running for president. instead, he announced he would step down because of an extramarital affair. at a time when the cia was under fire for all it didn't know about the attack on benghazi, it is a huge step for the newly re-elected president, and a profound personal failing for an officer who has given so much to his country. we begin tonight with nbc's andrea mitchell who broke the story, in our d.c. news room. >> reporter: good evening, his resignation because of an extramarital affair sent shock waves through the administration. the cia has been under fire, but this had nothing to do with benghazi or politics. it was entirely personal. he was a four-star, the best known warrior of his generation, leader of combat forces in iraq and afghanistan before his commander-in-chief asked him to retire from the military and leave the cia. >> i